<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<h3>HTML Form Attributes</h3>
<h3>Readonly Attribute </h3>
<form>
    Email:
    <input type="text" name="email"><br>
    Country:
    <input type="text" name="country" value="Norway" readonly>
    <br>
</form>
<hr>
<h3>Disabled Attribute </h3>
<form>
    First name:
    <input type="text" name="fname"><br>
    Last name:
    <input type="text" name="lname" value="Wang" disabled>
    <br>
    <input type="checkbox" id="vehicle" disabled>
    <label for="vehicle">I have a bike</label> <br>
    <select disabled>
        <option></option>
        <option>Volvo</option>
        <option>Saab</option>
        <option>Opel</option>
        <option selected>Audi</option>
    </select>
</form>
<hr>
<h3>Placeholder Attribute </h3>
<form>
    <input type="text" placeholder="请输入用户名">
    <br><input type="password">
</form>
<hr>
<h3>Required Attribute </h3>
<form>
    <input type="text" required><br>
    <input type="checkbox" id="vehicle2" required>
    <label for="vehicle2">I have a bike</label> <br>
    <select required>
        <option value="">None</option>
        <option value="1">Volvo</option>
        <option value="2">Saab</option>
        <option value="3">Mercedes</option>
        <option value="4">Audi</option>
    </select><br>
    <button type="submit">Submit</button>
</form>

</body>
</html>